Three-state electronic circuit



Aug. 25, 1959 E. L. WOLF THREE-STATE ELECTRONIC 'CIRCUIT Filed Jan. 14,1957 PULSE OUTPUT INVENTOR. EDWARD L. WOLF ATTORNEY United States PatentTHREE-STATE ELECTRONIC CIRCUIT Edward L. Wolf, Fairport, N.Y., assignorto General Dynamics Corporation, Rochester, N.Y., a corporation ofDelaware Application January 14, 1957, Serial No. 633,988

4 Claims. (Cl. 30788.5)

The present invention relates to indicating and counting circuits and,more particularly, to an electronic circuit for indicating or countingthe relative order of occurrence of discrete electrical pulses.

Scaling circuits for counting or indicating the relative order ofoccurrence of electrical pulses are well known. Usually, the countingcircuit is either a decimal type or a binary scale of two type. Thereare, however, occasions when a so-called trinary circuit having ascaling factor of three to indicate or count the relative order ofdiscrete pulses would be advantageous.

It is a principal object of this invention to provide a three-stateelectronic circuit which may be used to indicate the relative order ofoccurrence of discrete electrical pulses on a scale of three basis.

It is also an object of this invention to provide a threestateelectronic circuit which may be used as a scale of three countingcircuit to provide one electrical pulse output signal for each thirdelectrical input pulse applied to the circuit.

Yet another object of the invention is to provide an improved pulseindicating or counting circuit which is extremely simple in form anduses inexpensive gas tube diode components.

Further objects and advantages of the invention will be apparent withreference to the following specification and drawing in which the singlefigure is a schematic wiring diagram of a three-state electronic circuitembodying the principles of the invention.

Referring to the drawing, a single stage of a threestate electroniccircuit may be comprised of a pair of gas tube diodes and 11 which maybe of the well known type identified as NE-96. The NE-96 gas tube diodeis a neon diode constant current device which requires a direct currentpotential of approximately one hundred and thirty volts or morethereacross to become conductive, but which will sustain conduction witha direct current potential thereacross of approximately sixty-five toseventy volts. A battery 12, having its negative terminal grounded, isconnected to supply operating potentials for the circuit, as will bedescribed in detail. Pulse input terminals 13 and 14, one of which isconnected to ground, and pulse output terminals 15 and 16, one of whichis connected to ground, are provided for applying the discrete inputpulses to be counted and connecting to the output pulse, respectively.The parameters of the circuit elements are selected to be such thatdiscrete pulses to be counted having a certain minimum amplitude willcause the desired operation of the circuit, while the output pulse maybe of any suificient amplitude or characterization for use to indicateor to be subsequently amplified or modified for connection to subsequentelectronic circuits.

The neon diode 10 is connected in series with resistors and 21 and thebase and emitter of transistor 22 across the positive and negativeterminals of the battery 12. The back resistance value of the transistor22 and the values of resistors 20 and 21 together with the amplitude ofvoltage supplied by battery 12 provide that the direct current potentialnormally applied across the electrodes of the diode 10 is ofinsufficient value to cause the diode 10 to fire and become conductive.According to the teachings of this invention, the value of theabove-referred to potential normally maintained across the diode 10 isless than the firing potential for the diode 10 by an amount which isalso less than the predetermined minimum amplitude of the pulses to beindicated as connected across the pulse input terminals 13 and 14.

Similarly, the diode 11 is connected in series with resistors 23 and 24across the positive and negative terminals of the battery 12 and thearrangement is such that the potential normally across the diode 11 isinsuflicient to cause the diode 11 to fire and become conductive, butyet is not lower than the firing voltage for the diode by an amountgreater than the minimum amplitude for the pulse to be counted whenapplied across input terminals 13 and 14. However, resistors 25 and 2.6interconnect the energizing circuits for diodes 10 and 11 in such mannerthat the potential normally across diode 10 is somewhat greater than thepotential across diode 11. This is important to assure the properfunctioning of the circuit as will become apparent when the operation ofthe circuit is subsequently described.

The discrete voltage pulses to be counted are connected across the inputterminals 13 and 14 and are coupled through a difierentiating couplingnetwork, including resistors 30, 31 and capacitors 32, .33 and 34, inparallel to both of the energizing networks for diodes 10 and 11. Thisarrangement is such that the diiferentiating action causes the inputpulses to be counted to momentarily add to the potentials normallyapplied across both gas tubes 10 and 11 when neither gas tube isconducting. However, since the potential normally applied across gastube 10 is higher than the potential applied across gas tube 11, themomentary increase of potential across diode 10 will exceed the firingpotential of that tube before the momentary increase in potential acrossgas tube 11 reaches its firing potential value. Therefore, assuming thatneither gas tube 10 or 11 is at first conducting, and assuming that theamplitude of the discrete voltage pulse to be counted is greater thanthe minimum value to add to the potential normally across either diodetube 10 or 11 to thereby exceed the firing voltage for such diodes, thegas tube diode 10 only will fire for the first input pulse and, infiring, will become conductive to cause current to flow through thetransistor 22 and resistors 20 and 21. It is inherent in the circuitarrangement, as described, that as soon as gas tube 10 fires, the inputpulse energy is absorbed so that the potential across gas tube 11 cannotcontinue to increase to the point where gas tube '11 would becomeconductive, bearing in mind that the potential normally applied acrossgas tube 11 is lower than that of gas tube 10 as stated above. Thesubsequent flow of current through the transistor 22 will produce apulse output across the output network, includin gthe resistors 35, 36and capacitor 37, to the pulse output terminals 15 and 16. Thus, theapplication of the first discrete pulse to be counted is indicated orcounted by the conduction of gas tube 10 and the appearance of adistinctive pulse across the output terminals 15 and 16.

The second discrete voltage pulse to be indicated or counted as appliedacross terminals 13 and 14 and through the difierentiating network,including capacitors 32-34, will raise the amplitude of potential acrossdiode 11 sufliciently to cause such tube to become conductive and, suchtube in becoming conductive, will, through the network including thecapacitor 34 and resistors 25 and 26, produce a negative pulse acrossthe diode 10 sufiicient to momentarily lower the potential thereacrossbelow the sustaining voltage amplitude value thereby extinguishing diode10. Note that the amplitude of potential across tube cannot be'raisedappreciably by the secondpulse since that tube is already conducting;Thus; the appli cation of the second discrete voltage pulse across inputterminals 13 and 14 causes gas tube 10 tobe extinguished and=gastube 11'to become conductive"therebyindicating the-occurrence of the secondpulse: V,

When the third discrete voltage pulse is appliedacross the inputterminals 13' and 14f to be connected by the differentiating network,includingcoupling capacitors 32 and 33, across the diode 11, since thediodell isthen conducting, the voltage thereacross cannot. momentarilyincrease to any extent. However, upon theidecay of the third inputpulse, a'negative pulse will he produced'across the diode 11 due to theaction of thedifferentiatingcircuit and this negative pulse isofsuflicient amplitude tolower the potential across diode 11 below theminimum sustaining-voltage amplitude value sothatdiode 11' is therebyextinguished. Thus, the application of the third discrete pulse-causesthe then conducting diode 11' to become extinguished so that anindication of the third pulse is obtained when neither diode 10'or 11 isconductive.

Thereafter, the fourth voltagepulse will again. cause diode 10 to becomeconductive, as previously described inconnection with the application ofthe first input pulse to' be counted, and will likewise produce adistinctive output pulse across terminals 15 and 16. Therefore, thecircuit, including the gas tube diodes 10" and 11", functions to providethree different indication statesfor the relative occurrence: of threediscrete'voltage pulses and also functions as a scale of three countercircuit since a' single output pulse is provided for each'third inputpulse.

The following table of values may be givenfor atypical application ofthe circuit usingNE-96 gas tube diodes and with a-maximum potentialof-one hundred andforty' Minimum amplitude for input pulse 150 volts.

The values for the pulse output circuit,- including-the transistor 22,resistors 35, 36 and capacitor 37, are suitably selected depending uponthe choice of transistor 22 and would be obvious to anyone skilled inthe art; Al-

though the network, including resistors' 25-ai1d26,-has

been specifically described for providing the relative difference inapplied voltages across the respective diodes 10 and 11, it should beobvious that many other circuit arrangements may be provided to obtain'the desired'difference in normal potential across the diode's'10and 11and that, therefore, the invention and the appended claims are notlimited to this specific circuit arrangement. Variousmodifications willoccur to'thoseskilled'in the art;-

What is claimed is:

1. A circuit for indicating the relative order of occurrence of discretepulses having a voltage amplitude at least equal to a predeterminedminimum and comprising, first and second constant current gaseous "diodedevices, means to apply a voltage across each device that'is' lower thanthe firing potential ofeach' device by an amount that is less than thepredetermined minimum amplitude of the pulses to be indicated andwith'the-voltage across said first device greater than the voltageacross said second device, a source ofpuls'es'to be indicated, and

means including a differentiating coupling network-for connecting thesource of pulses to be indicated across the anode electrodes of each ofsaid devices in a manner to add to and increase the voltages across saiddevices to thereby cause said first device to become conductive whenneither of said devices are conducting, to thereby cause said seconddevice to become conductive and extinguish said first device when saidfirst device is conducting, and to thereby extinguish said second devicewhen said second device is conducting, the relative states of conductionof said devices being indicative of the relative order of occurrence ofpulses.

2. A circuit for indicating the relative order of occurrence of discretepulses having a voltage amplitude at least equal to apredetermined'minimum and'comprising, a pair of pulse inputterminals,first and second'constant current gaseous two-electrode devices, meansto apply a voltage across each device that is lower than the firingpotential of each device by an amount that is lessthan the predeterminedminimum amplitude of the pulses to be indicated and with the voltageacross said first device greater than the voltage across said seconddevice, a source of pulses to be indicated, and means includingadifferentiating coupling network for connecting'the source of pulses tobe indicatedacross" the anode'electrodes' of each" of said devices in amanner to'add to an'dincrease the voltages across said devices to;thereby cause said first device to'becom'e conductive when'neither' ofsaid devices are conducting, to thereby cause 'said'seconddeivice tobecome conductive and'extin'guishsaid first device when saidfirst-device is conducting, andtotherebyex tinguish said'second devicewhen said secondhdevice'is" conducting, said coupling networkc'omprising1at least" one capacitor in a series circuit'b'et'ween' one'of' said terminals and one'of'the'electrodes of said second devicetogether with at least one capacitor in'aserie's'ci'rcuit between saidone electrode of the second device and an" electrode of said firstdevice, the relative state'sof conduction of' said devices beingindicativeof the-relative order of occurrence of pulses.

3. A scale of three circuit for counting discrete pulses having avoltage amplitude at least equal to a predeterfl mined minimum andcomprising, first and second constant current diode devices, means toapply a voltage across each device that is 'less than'the firingpotential of each' device by an amount thatis lower than thepredetermined minimum amplitude of the pulses .to be counted and withthe voltage across said first device greater thanthe voltage across saidsecond device, asource' of'pulses who indicated, means including adifferentiatingcoupling network for connecting the source of pulses tobecounted' across the anode electrodes of each'of said devices in'amanner to add to and increase'the voltages across said devices tothereby cause said first deviceto become: con

ductive when neither of said devices are conducting, to thereby causesaid second device to become-conductive and extinguish said first devicewhen'saidfirst device is" conducting, and to thereby extinguish saidsecond device when said second device is conducting, and meansto producea count signal responsive to currentflow through one of's'aid devices tothereby counteach third successive pulse: 7 V M 4. A scale of threecircuit for'counting discrete pulses having a voltage'amplitude at leastequal to fa predeter-' mined minimum and comprising', apair of pulseinput terminals, first and second'constant current gaseous two electrodedevices-means to' apply avoltage acrosseach devicethat is lowerthan'the'fi ring potential of each;

device by an amount'that-is less than the-predeterminedminimum'amplitude of the pulses to be counted and with thevoltage-across said first device gr eat'er'than the voltage across'saidsecond devicefa'sourceof pulses *to' be" indicated, means including adiflFerentiat-ing-"couplin'g network for connecting-thesourceof pulsesto' be counted across the anode electrodes 'of"eachoffsaiddevices in a"thereby cause said second device to become conductive and extinguishsaid first device when said first'devi'ce'is conducting, and to therebyextinguish said second device when said second device is conducting,said coupling network comprising at least one capacitor in a seriescircuit between one of said terminals and one of the electrodes of saidsecond device together with at least one capacitor in a series circuitbetween said one electrode of the second device and an electrode of saidfirst device, the relative states of conduction of said devices beingindicative of the relative order of occurrence of pulses and meansReferences Cited in the file of this patent UNITED STATES PATENTSWilliams et a1 Apr. 15, 1952 Green Dec. 20, 1955 Morris Apr. 2, 1957

